Hollow heat-recoverable articles have generally been produced by forming a polymer into the desired heat-stable configuration, simultaneously or subsequently crosslinking the polymer in its heat-stable configuration, heating and then deforming the article, and then cooling the article while in the deformed state so that the deformed configuration is retained. In use, since the deformed state of the article is heat-unstable, application of heat will cause the article to revert or tend to revert to its original heat-stable configuration. Further, as a result of cross-linking, the article may be heated to a temperature considerably above its melting point without melting the article.
When it is desired to provide such articles with inserts, it has frequently been necessary to load such inserts after the completion of the article on an item-by-item basis, e.g. by way of a manual or semi-automatic finishing process. Even when automatic or continuous methods have been available, e.g. in the case of articles coated internally by coextrusion methods, such manufacture is relatively expensive. Frequently, however, the hollow articles are of such a configuration that they cannot be produced directly by extrusion, such as when they are of non-constant cross-section along any axis thereof. For example, boots, udders (as used herein the term udder refers to an article comprising a plurality of intersecting hollow regions employed in the termination of electrical cables, and also commonly referred to as cable "breakouts"), end-caps, or the like articles have been formed into the desired heat stable configuration on an item-by-item basis by moulding, e.g. by injection, compression or transfer moulding techniques.
Previously it has been known that one may form a hollow, generally tubular connector device having solder therein and wherein substrates such as electrical wires may be inserted in the connector device, so that, upon application of heat, the hollow device collapses and the solder fuses, thereby connecting the substrates as is generally set forth in U.S. Pat. No. 3,243,211.
However, as is well known, one must insert the working matter usually by hand or, at the very best, by a semi-automatic process in order to form the fusible connector. As can be appreciated, such manual labor is quite expensive. However, since it is well known that heat recoverable (substantially cross-linked) sheets do not readily bond, there has been no other alternative. In order to make a device which was heat recoverable, such as that of U.S. Pat. No. 3,243,211, the hollow connector had to be crosslinked and expanded prior to the insertion of the insert.
It had always been considered that if cross-linked material could be bonded together the problem would be solved. The solution would then simply be to have one sheet stamped or printed with solder in a predetermined manner. The second sheet could then be fused over the first sheet and a heat recoverable connector having solder in an appropriate pattern could thus be formed by an automatic process.
As is well known, however, it has heretofore been considered impossible to fuse together two substantially cross-linked sheets.
U.S. Pat. No. 3,396,894 discloses the packaging of metered amounts of flux and solder in a heat-recoverable preformed sheet which forces the solder into place.
It may be noted that this patent is not a hollow connector but comprises merely one sheet of material imprinted with solder.
U.S. Pat. No. 3,721,749 discloses a multiple connection device having open ends formed from two identical sheets. Upon heat recovery the working zones collapse towards one another causing the inserts to be enclosed. Applicant's invention allows the inserts to remain at approximately the same distance from one another throughout the entire heat recovery process without movement by both sheets.